Determination of the complex elastic moduli of materials using a "free-free" bar technique

The objective of this research is to investigate the dynamic elastic properties of materials and their temperature and frequency dependence using an acoustic resonance based method. In this technique, the torsional, flexural, and/or longitudinal vibrational modes of a 'free-free' bar are s...

Full description

Bibliographic Details
Main Author: Bartlett, David L.
Other Authors: David A. Brown
Language:en_US
Published: Monterey, California. Naval Postgraduate School 2013
Online Access:http://hdl.handle.net/10945/30871
id ndltd-nps.edu-oai-calhoun.nps.edu-10945-30871
record_format oai_dc
spelling ndltd-nps.edu-oai-calhoun.nps.edu-10945-308712014-11-27T16:17:46Z Determination of the complex elastic moduli of materials using a "free-free" bar technique Bartlett, David L. David A. Brown Gardner, David L. NA NA Engineering Acoustics The objective of this research is to investigate the dynamic elastic properties of materials and their temperature and frequency dependence using an acoustic resonance based method. In this technique, the torsional, flexural, and/or longitudinal vibrational modes of a 'free-free' bar are selectively excited and tracked as a function of temperature. The resonance frequency of the torsional model is used to obtain the dynamic shear modulus. The dynamic Young's modulus is obtained from either the resonance frequency of the flexural or longitudinal mode of the bar. The quality factor, Q, of each mode is measured to obtain the damping properties of the material. A phase-locked-loop (PLL) is used to track the resonance frequency as a function of changing temperature for the particular vibrational model selected. Using this technique, the storage modulus and loss tangent may be obtained in a continuous fashion. Materials tested in this thesis include: Polyurethane PR-1592, a common sonar encapsulant, Polymethyl Methacrylate (PMMA) or plexiglass, and Polycarbonate. This research encompasses the theory, accuracy, limitations and applications of this measurement technique. 2013-04-26T18:59:22Z 2013-04-26T18:59:22Z 1994-03 Thesis http://hdl.handle.net/10945/30871 en_US This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. As such, it is in the public domain, and under the provisions of Title 17, United States Code, Section 105, it may not be copyrighted. Monterey, California. Naval Postgraduate School
collection NDLTD
language en_US
sources NDLTD
description The objective of this research is to investigate the dynamic elastic properties of materials and their temperature and frequency dependence using an acoustic resonance based method. In this technique, the torsional, flexural, and/or longitudinal vibrational modes of a 'free-free' bar are selectively excited and tracked as a function of temperature. The resonance frequency of the torsional model is used to obtain the dynamic shear modulus. The dynamic Young's modulus is obtained from either the resonance frequency of the flexural or longitudinal mode of the bar. The quality factor, Q, of each mode is measured to obtain the damping properties of the material. A phase-locked-loop (PLL) is used to track the resonance frequency as a function of changing temperature for the particular vibrational model selected. Using this technique, the storage modulus and loss tangent may be obtained in a continuous fashion. Materials tested in this thesis include: Polyurethane PR-1592, a common sonar encapsulant, Polymethyl Methacrylate (PMMA) or plexiglass, and Polycarbonate. This research encompasses the theory, accuracy, limitations and applications of this measurement technique.
author2 David A. Brown
author_facet David A. Brown
Bartlett, David L.
author Bartlett, David L.
spellingShingle Bartlett, David L.
Determination of the complex elastic moduli of materials using a "free-free" bar technique
author_sort Bartlett, David L.
title Determination of the complex elastic moduli of materials using a "free-free" bar technique
title_short Determination of the complex elastic moduli of materials using a "free-free" bar technique
title_full Determination of the complex elastic moduli of materials using a "free-free" bar technique
title_fullStr Determination of the complex elastic moduli of materials using a "free-free" bar technique
title_full_unstemmed Determination of the complex elastic moduli of materials using a "free-free" bar technique
title_sort determination of the complex elastic moduli of materials using a "free-free" bar technique
publisher Monterey, California. Naval Postgraduate School
publishDate 2013
url http://hdl.handle.net/10945/30871
work_keys_str_mv AT bartlettdavidl determinationofthecomplexelasticmoduliofmaterialsusingafreefreebartechnique
_version_ 1716725119632539648